The Fischer-Tropsch synthesis reaction involves converting a reactant composition comprising H2 and CO in the presence of a catalyst to aliphatic hydrocarbon products. The reactant composition may comprise the product stream from another reaction process such as steam reforming (product stream H2/CO˜3), partial oxidation (product stream H2/CO˜2), autothermal reforming (product stream H2/CO˜2.5), CO2 reforming (H2/CO˜1), coal gasification (product stream H2/CO˜1), and combinations thereof. The aliphatic hydrocarbon products may range from methane to paraffinic waxes of up to 100 carbon atoms or more.
Conventional reactors such as tubular fixed bed reactors and slurry reactors have various problems in heat and mass transfer resulting in limitations of choice of process conditions for Fischer-Tropsch synthesis reactions. Hot spots in the fixed bed reactors significantly promote methane formation, reduce the heavy hydrocarbon selectivity and deactivate the catalyst. On the other hand, strong mass transfer resistance inherent in a catalyst suspended in a slurry system generally reduces the effective reaction rate and also causes difficulty in separation of catalysts from the products. This invention provides a solution to these problems.
This invention relates to a process for conducting a Fischer-Tropsch synthesis reaction in a microchannel reactor wherein the one-pass conversion of CO within the reactor is enhanced and the selectivity to methane is reduced. With the inventive process the tendency to form hot spots in the microchannel reactor is reduced. This reduction in the tendency to form hot spots is believed to be due, at least in part, to the fact that the microchannel reactor provides enhanced heat transfer characteristics and more precise control of temperatures and residence times as compared to prior art processes wherein microchannel reactors are not used. With this process, it is possible to obtain relatively high levels of conversion of the CO and high levels of selectivity to the desired product (e.g., hydrocarbons in the middle distillate range) as compared to such prior art. A novel catalyst as well as a novel microchannel reactor design are provided.